Tuning the localized dissolution environment of polysulfides for practical Li-S cells

Abstract

The shuttle effect of soluble polysulfides is one of the main reasons for the poor cycling performance, which greatly impedes the practical application of lithium-sulfur (Li-S) batteries. In this context, we report a novel design of sulfur cathode structure by regulating the distribution of PEO on the surface of C/S particles to extend the stable cycle life of practical Li-S cells. The in-situ dissolution of PEO changes the localized solution environment around C/S particles and suspends the diffusion of polysulfides (LiPSs), while the large number of mesopores retained inside C/S particles can ensure the good infiltration of electrolyte and act as a container for LiPSs. With this strategy, the cycle performance of the high sulfur loading (∼4 mg cm−2) Li-S pouch cell is significantly improved, with a discharge-specific capacity above 900 mAh g−1 and a capacity retention rate of 91.68% for 70 cycles. In addition, the rate performance of pouch cells is quite significant due to the promotion of local kinetic conversion (736.4mAh g−1 at 2C). At last, the Ah-scale Li-S pouch cell exhibits excellent capacity (above 1000 mAh g−1), low fading (0.16% per cycle), and high power capability. This work offers a new perspective for the design of sulfur cathode structures and promotes the scale-up of lithium-sulfur cells for practical applications.